German Published Patent Application No. 197 48 764 describes an initial quantity for producing weldable organic coil coatings. Beside the normal organic components, which later form the matrix of the coating by curing and/or mutual cross-linking, the initial solids mixture has, as additive pigments in quantities between 40 and 70% zinc and/or aluminum and/or graphite and/or molybdenum disulfide and/or soot and/or iron phosphide. The additive pigments are used at least partially for the improvement or implementation, as the case may be, of an electrical conductivity of the initial solid mixture, with which a coil coating method first becomes possible.
In this method, used particularly in the metal working industry, the initial solid mixture is deposited onto a substrate, e.g., broad strip, and cured, whereby the latter becomes pre-coated. On account of this, savings in method steps and cleaning steps are possible, for example, in automobile manufacturing, since the coating can be a corrosion protection primer, by which the pre-treated sheet metal, made, for example, of steel, galvanized and/or other pre-treated steel, or of aluminum is protected from corrosion. The desired pre-coated sheet metal parts are formed, stamped, the parts obtained are joined using diverse methods such as welding, bonding, riveting, crimping, and after that, the joined part, for instance, a vehicle body or parts thereof, are conveyed to an operation for further coating.
However, in the case of an initial solids mixture, the addition of iron phosphide carries with it the danger of phosphane (PH3) development, in the case of hydrolysis and combustion, which does not have an inconsiderable toxicity, and also that iron phosphide has a not inconsiderable cost price. Furthermore, in the case of environmentally friendly water being used as solvent, the risk of hydrolysis always exists.
It is an object of the present invention to provide an initial solids mixture to the extent that in a coil coating method an aqueous based, or at least a water-containing adhesive agent system may be used.